/Engine/Source/Runtime/SlateCore/Public/Widgets/SCompoundWidget.h
A CompoundWidget is the base from which most non-primitive widgets should be built. CompoundWidgets have a protected member named ChildSlot.
class SCompoundWidget : public [SWidget](API\Runtime\SlateCore\Widgets\SWidget)
FCompoundWidget...
ChildSlot
The slot that contains this widget's descendants.